Apparatus and method for implanting an electrical lead

ABSTRACT

An electrical lead includes a coil disposed at a distal end of the electrical lead, the coil having an undulated shape in its free state and a fixation electrode disposed on and electrically coupled with the coil. The electrical lead further includes a pace/sense electrode disposed on the coil distally from the fixation electrode and electrically isolated from the coil and a conductor extending to the pace/sense electrode and disposed external to the coil. A method for implanting an electrical lead includes positioning the electrical lead within a vessel, positioning a fixation electrode of the electrical lead into contact with the vessel, and emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention generally relates to an implantable medical device and, in particular, to a method and apparatus for anchoring vasculature leads using radio frequency energy.

[0003] 2. Description of the Related Art

[0004] Since the introduction of the first implantable pacemakers in the 1960s, there have been considerable advancements in both the fields of electronics and medicine, such that there is presently a wide assortment of commercially available body-implantable electronic medical devices. The class of implantable medical devices now includes therapeutic and diagnostic devices, such as pacemakers, cardioverters, defibrillators, neural stimulators, and drug administering devices, among others. Today's state-of-the-art implantable medical devices are vastly more sophisticated and complex than their early counterparts, and are capable of performing significantly more complex tasks. The therapeutic benefits of such devices have been well proven.

[0005] Modern electrical therapeutic and/or diagnostic devices for the heart require a reliable electrical connection between the device and a region of the heart. Typically, a “lead” is used to electrically couple the therapeutic and/or diagnostic device to a portion of the heart. One type of commonly used implantable lead is a transvenous lead, which is generally positioned through the venous system to a location proximate the heart. At their proximal end, they are typically connected to the electrical therapeutic and/or diagnostic device, which may be implanted. Such leads normally take the form of a long, flexible, insulated conductor. Among the many advantages of transvenous leads is that they permit an electrical contact with the heart without physically exposing the heart itself, i.e., major thoracic surgery is not required.

[0006] In certain circumstances, it is particularly advantageous to finally position such leads within vasculature proximate the heart, such as within a coronary sinus, a coronary vein, or the like. Once optimally positioned, it is desirable for the lead, and thus the electrode or electrodes that are part of the lead, to remain in a set position. Movement of the electrode or electrodes relative to the portion of the heart to be affected by electrical stimuli emitted from the electrode or electrodes may result in the stimuli having an inadequate effect on the heart. Further, if the electrode or electrodes are allowed to move, another portion of the heart may inadvertently and undesirably be stimulated.

[0007] Leads have been developed that include features for holding the leads in place within vasculature, such as tines and screws. Tined leads may generally cause little tissue damage within the vasculature and may have lower pacing thresholds than screw leads, but they can only be used in trabeculated structures, and they can ensnare the chordae tendineae during placement. Screw-type leads do not generally require trabeculae for fixation, but the screw may move with the lead causing localized tissue trauma and an increased pacing threshold. Further, screwing leads into structures that are parallel to the longitudinal axis of the lead may be difficult.

[0008] The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.

SUMMARY OF THE INVENTION

[0009] In one aspect of the present invention, an electrical lead is provided. The electrical lead includes a coil disposed at a distal end of the electrical lead, the coil having an undulated shape in its free state and a fixation electrode disposed on and electrically coupled with the coil. The electrical lead further includes a pace/sense electrode disposed on the coil distally from the fixation electrode and electrically isolated from the coil and a conductor extending to the pace/sense electrode and disposed external to the coil.

[0010] In another aspect of the present invention, a method for implanting an electrical lead is provided. The method includes positioning the electrical lead within a vessel, positioning a fixation electrode of the electrical lead into contact with the vessel, and emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.

[0011] In yet another aspect of the present invention, a method for implanting an electrical lead is provided. The method includes positioning the electrical lead within a vessel; partially withdrawing a stylet, inserted within a lumen of the electrical lead, to allow a portion of the electrical lead to become undulated such that a fixation electrode of the electrical lead is in contact with the vessel; and emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, and in which:

[0013]FIG. 1 is a stylized diagram of an implantable medical device according to the present invention;

[0014]FIG. 2 is a stylized top view of an electrical lead according to the present invention;

[0015]FIG. 3 is a stylized side view of the electrical lead of FIG. 2;

[0016]FIG. 4 is a stylized cross-sectional view of the electrical lead of FIG. 2 taken along the IV-IV line in FIG. 2;

[0017]FIG. 5 is a stylized cross-sectional view of the electrical lead of FIG. 2 taken along the V-V line in FIG. 2;

[0018] FIGS. 6-8 are stylized side views of the electrical lead of FIG. 2 as it is implanted in a vessel.

[0019] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0020] Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0021] Embodiments of the present invention concern body-implantable medical devices, such as the device 100 illustrated in FIG. 1, having single or multiple leads, such as a lead 102, extending from a control unit 104 to one or more pace/sense electrodes 106 and to one or more fixation electrodes 108. The pace/sense electrode 106 may be used to stimulate a tissue of the body and/or sense one or more conditions in the tissue. The fixation electrode 108 may be used to anchor the lead 102 to the tissue, such as within vasculature 110 (e.g., a coronary sinus, a coronary vein, a cardiac vein, or the like), as will be described later. The lead 102 further includes an undulated portion 112, which urges the electrodes 106, 108 into intimate contact with the tissue, such as the vasculature 110.

[0022] Examples of such implantable medical devices are implantable coronary pacing devices, pulse generators, defibrillators, neural stimulation devices, electrogram devices, and the like. Generally, these devices operate by monitoring one or more conditions in the tissue and/or by delivering electrical stimuli to the tissue via the lead or leads. For example, such devices may be used to sense cardiac activity, to deliver electrical pacing stimuli to a portion or portions of a heart, to deliver electrical defibrillating stimuli to a portion or portions of the heart, to deliver electrical stimuli to a nerve, to deliver electrical stimuli to a portion or portions of a nerve bundle, or to deliver electrical stimuli to a portion or portions of a brain. While the description provided herein is directed to an implantable medical device used in a coronary setting, the present invention encompasses any implantable medical device, such as those described above, used in any setting.

[0023] According to the present invention, radio frequency (RF) energy, similar to that used in RF ablation, is emitted from the fixation electrode 108. The interaction of this energy with the tissue proximate the fixation electrode 108 causes the tissue proximate the fixation electrode 108 to adhere to the fixation electrode 108. Such a method and apparatus for fixating the lead 100 to the vasculature 110 has advantages over tines and screws in that the lead can be secured to any tissue and has no tines to catch in the chordae tendineae.

[0024] FIGS. 2-5 illustrate an embodiment of an implantable electrical lead according to the present invention. FIG. 2 illustrates a top view of an electrical lead 200 and FIG. 3 illustrates a side view of the lead 200. FIG. 4 depicts a cross-sectional view of the lead 200. The lead 200 extends from a control unit (e.g., the control unit 104 or the like) and includes an undulated shaped portion 302, as shown in FIG. 3. In one embodiment, the undulated shaped portion 302 has a shape generally corresponding to a sinusoidal-like shape. The undulated shaped portion 302 includes a coil 204 having the desired undulated shape, at least in part. The coil 204 is electrically coupled to a fixation electrode 206, as illustrated in FIG. 5, and defines a lumen 402, shown in FIG. 4, adapted to receive a stylet (not shown in FIGS. 2-5), which is used to position the lead 200 within vasculature, a coronary vein, a coronary sinus, or the like and as a pathway for fixation energy to anchor the lead 200, as described below.

[0025] In one embodiment, the coil 204 is made of wound nickel-cobalt-chromium superalloy wire, such as MP35N, insulated with, for example, a modified polyvinyl acetal polymer (e.g., Formvar® or the like), a polyimide polymer (e.g., Pyre ML® or the like), or a fluoropolymer (e.g., Teflon@, polytetrafluoroethylene, or the like). The present invention, however, is not so limited but rather encompasses the coil 204 being made of any desired material or materials. A portion of the insulation of the coil 204 adjacent to the lumen 402 is removed so that the stylet may make electrical contact with the coil 204.

[0026] The lead 200 further includes an electrically insulated conductor 208 extending from the control unit, via a body 210 of the lead 200 and external to the coil 204, to a pace/sense electrode 212 for conducting pacing and/or sensing signals between the control unit and the pace/sense electrode 212. The scope of the present invention encompasses, however, an embodiment wherein the body 210 extends proximate a distal end 214 of the coil 204 surrounds the coil 204 and the conductor 208. Unlike the fixation electrode 206, the pace/sense electrode 212 is electrically isolated from the coil 204.

[0027] As shown in FIG. 5, an insulating layer 502 electrically insulates the inner surface of the fixation electrode 204 and an insulating layer 504 electrically insulates the outer surface of the fixation electrode 204, except for an electrical connection with the coil 204 and an active surface 506 that protrudes through the insulating layer 504. Fixation energy is transmitted to surrounding tissue through the active surface 506. In one embodiment, the pace/sense electrode 212 has a construction corresponding to that of the fixation electrode 204, except that no electrical connection is made between the pace/sense electrode 212 and the coil 204.

[0028] FIGS. 6-8 illustrate the implantation of the lead 200 within a vessel 602. FIG. 6 depicts the lead 200 configured such that it may be inserted into the vessel 602. FIG. 7 illustrates the lead 200 at a midpoint during its implantation within the vessel 602. FIG. 8 shows the lead 200 as it is finally implanted in the vessel 602. A stylet 604 is inserted into the lumen 402 (shown in FIGS. 4 and 5) and advanced to straighten the lead 200, as shown in FIG. 6. A catheter (not shown) may be inserted into the vessel 602 to provide a pathway for guiding the lead 200 during implantation. The lead 200 is fed into the vessel 602, either within the catheter or omitting the use of the catheter, to a desired position for the pace/sense electrode 212. The stylet 604 is then retracted from the lumen 402 a predetermined distance, as illustrated in FIG. 7, to allow a portion of the coil 204 to return to its undulated shape, thus urging the pace/sense electrode 212 against the vessel 602. In one embodiment, the stylet 604 has a marking 702 indicating the proper distance to retract the stylet 604. The stylet 604 may be used to rotate the lead 200 so that the pace/sense electrode 212 is in intimate contact with a desired portion of the vessel 602, such as the myocardial side of the vessel 602.

[0029] Various techniques are available to determine when the pace/sense electrode 212 is in intimate contact with the myocardial side of the vessel 602. For example, the pacing threshold generally is lower when the distance to viable tissue is shorter, such as when the pace/sense electrode 212 is facing the myocardium. Further, the pacing impedance may generally be lower when the pace/sense electrode 212 is facing the myocardium as opposed to the pericardium, since the impedance is influenced by the conductivity of the material proximate the surface of the pace/sense electrode 212. For example, the impedance of fat is about 1000 ohm-cm, the impedance of muscle is about 450 ohm-cm, and the impedance of blood is about 150 ohm-cm. The integrity of the contact between the pace/sense electrode 212 and the vessel 602 may be determined by evaluating the impedance level.

[0030] Further, the width and/or amplitude of the QRS complex may be used as an indicator of the position of the pace/sense electrode 212. As the active surface 506 move further away from the myocardium, the signal amplitude of the QRS complex generally decreases and the pulse width of the QRS complex generally increases.

[0031] Once the pace/sense electrode 212 is positioned as desired, the stylet 604 is withdrawn from the lumen 402 a predetermined distance, as illustrated in FIG. 8, to allow the remaining portion of the coil 204 to return to its undulated shape, thus urging the fixation electrode 206 against the vessel 602. In one embodiment, the stylet 604 has a marking 802 indicating the proper distance to retract the stylet 604. Techniques described previously to determine proper positioning of the pace/sense electrode 212 may also be applied to determining proper positioning of the fixation electrode 206. In one embodiment, the position of the pace/sense electrode 212 is rechecked after verifying proper positioning of the fixation electrode 206.

[0032] Once the electrodes 206, 212 have been properly positioned, a pulse generator 804, such as an ablation pulse generator or the like, is connected to the stylet 604 and to the patient via a skin patch 806, as illustrated in FIG. 8. A fixating pulse is then delivered to the fixation electrode 206. RF fixation of a lead is disclosed in U.S. Pat. No. 5,383,922 to Zipes et al., incorporated herein by reference in its entirety. Similar to the disclosure in Zipes et al., the energy required to fix electrode 206 will vary from design to design. However, fixation can generally be accomplished using a prior art RF electrosurgical power source within the range of power levels recommended for use in electrocoagulation. In particular, RF sensors equipped with impedance meter may be used to control the duration of application of the RF signal with a change of impedance in a given range known to indicate that fixation has occurred. Initial or temporary fixation may be accomplished with an RF signal terminated prior to the occurrence of the impedance change with permanent fixation being accomplished by extending the signal period with the change in impedance occurs. After fixation is accomplished, stylet 604 is removed from lumen 402.

[0033] The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. 

What is claimed is:
 1. An electrical lead, comprising: a coil disposed at a distal end of the electrical lead, the coil having an undulated shape in its free state; a fixation electrode disposed on and electrically coupled with the coil; a pace/sense electrode disposed on the coil distally from the fixation electrode and electrically isolated from the coil; and a conductor extending to the pace/sense electrode and disposed external to the coil.
 2. An electrical lead, according to claim 1, wherein the coil has a sinusoidal-like shape in its free state.
 3. An electrical lead, according to claim 1, wherein the coil is made from a nickel-cobalt-chromium superalloy.
 4. An electrical lead, according to claim 1, wherein the coil defines a lumen therein capable of receiving a stylet for transmitting fixation energy to the coil and for selectively restraining the coil in a non-undulated shape.
 5. An electrical lead, according to claim 1, wherein: the coil defines a lumen therein capable of receiving a stylet for selectively restraining the coil in an non-undulated shape; an insulating layer substantially covering the coil except in a portion facing the lumen such that an electrical energy may be transmitted from the stylet to the coil when the stylet is disposed within the lumen.
 6. A method for implanting an electrical lead, comprising: positioning the electrical lead within a vessel; positioning a fixation electrode of the electrical lead into contact with the vessel; and emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.
 7. A method, according to claim 6, further comprising urging a pace/sense electrode of the electrical lead into contact with the vessel.
 8. A method, according to claim 6, further comprising: urging a pace/sense electrode of the electrical lead into contact with the vessel; and determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned within the vessel.
 9. A method, according to claim 8, wherein determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon a pacing threshold.
 10. A method, according to claim 8, wherein determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon a pacing impedance.
 11. A method, according to claim 8, wherein determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon at least one of a width of a QRS complex and an amplitude of a QRS complex.
 12. A method according to claim 8, wherein emitting the electrical energy from the fixation electrode to the vessel further comprises emitting parameters of the fixation energy.
 13. A method for implanting an electrical lead, comprising: positioning the electrical lead within a vessel; withdrawing, at least partially, a stylet, the stylet being positioned within a lumen of the electrical lead, to allow a portion of the electrical lead to become undulated such that a fixation electrode of the electrical lead is in contact with the vessel; and emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.
 14. A method, according to claim 13, wherein partially withdrawing the stylet further comprises: withdrawing the stylet from the lumen through a first distance to urge a pace/sense electrode into contact with the vessel; determining if the pace/sense electrode is properly positioned; and withdrawing the stylet from the lumen through a second distance to urge the fixation electrode into contact with the vessel.
 15. A method, according to claim 13, wherein partially withdrawing the stylet further comprises: withdrawing the stylet from the lumen such that a first mark on the stylet is visible to urge a pace/sense electrode into contact with the vessel; determining if the pace/sense electrode is properly positioned; and withdrawing the stylet from the lumen such that a second mark on the stylet is visible to urge the fixation electrode into contact with the vessel.
 16. A method, according to claim 13, wherein positioning the electrical lead within the vessel further comprises positioning the electrical lead within the vessel such that a pace/sense electrode faces a myocardium.
 17. An apparatus, comprising: means for positioning the electrical lead within a vessel; means for urging a fixation electrode of the electrical lead into contact with the vessel; and means for emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.
 18. An apparatus, according to claim 17, further comprising means for urging a pace/sense electrode of the electrical lead into contact with the vessel.
 19. An apparatus, according to claim 17, further comprising: means for urging a pace/sense electrode of the electrical lead into contact with the vessel; and means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned within the vessel.
 20. An apparatus, according to claim 19, wherein the means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon a pacing threshold.
 21. An apparatus, according to claim 19, wherein the means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon a pacing impedance.
 22. An apparatus, according to claim 19, wherein the means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned further comprises means for determining if at least one of the pace/sense electrode and the fixation electrode is properly positioned based upon at least one of a width of a QRS complex and an amplitude of a QRS complex.
 23. An apparatus according to claim 19, wherein the means for emitting the electrical energy from the fixation electrode to the vessel further comprises means for emitting [parameters of the fixation energy].
 24. An apparatus for implanting an electrical lead, comprising: means for positioning the electrical lead within a vessel; means for partially withdrawing a stylet, inserted within a lumen of the electrical lead, to allow a portion of the electrical lead to become undulated such that a fixation electrode of the electrical lead is in contact with the vessel; and means for emitting an electrical energy from the fixation electrode to the vessel to anchor the electrical lead to the vessel.
 25. An apparatus, according to claim 24, wherein the means for partially withdrawing the stylet further comprises: means for withdrawing the stylet from the lumen through a first distance to urge a pace/sense electrode into contact with the vessel; means for determining if the pace/sense electrode is properly positioned; and means for withdrawing the stylet from the lumen through a second distance to urge the fixation electrode into contact with the vessel.
 26. An apparatus, according to claim 24, wherein the means for partially withdrawing the stylet further comprises: means for withdrawing the stylet from the lumen such that a first mark on the stylet is visible to urge a pace/sense electrode into contact with the vessel; means for determining if the pace/sense electrode is properly positioned; and means for withdrawing the stylet from the lumen such that a second mark on the stylet is visible to urge the fixation electrode into contact with the vessel.
 27. An apparatus, according to claim 24, wherein the means for positioning the electrical lead within the vessel further comprises means for positioning the electrical lead within the vessel such that a pace/sense electrode faces a myocardium. 